Interwoven manifolds for pressure drop reduction in microchannel heat exchangers

ABSTRACT

A microchannel heat exchanger coupled to a heat source and configured for cooling the heat source comprising a first set of fingers for providing fluid at a first temperature to a heat exchange region, wherein fluid in the heat exchange region flows toward a second set of fingers and exits the heat exchanger at a second temperature, wherein each finger is spaced apart from an adjacent finger by an appropriate dimension to minimize pressure drop in the heat exchanger and arranged in parallel. The microchannel heat exchanger includes an interface layer having the heat exchange region. Preferably, a manifold layer includes the first set of fingers and the second set of fingers configured within to cool hot spots in the heat source. Alternatively, the interface layer includes the first set and second set of fingers configured along the heat exchange region.

RELATED APPLICATIONS

This Patent application is a continuation in part of U.S. patentapplication Ser. No. 10/439,912, filed May 16, 2003, and entitled“INTERWOVEN MANIFOLDS FOR PRESSURE DROP REDUCTION IN MICROCHANNEL HEATEXCHANGERS”, hereby incorporated by reference, which claims priorityunder 35 U.S.C. 119 (e) of the co-pending U.S. Provisional PatentApplication Ser. No. 60/423,009, filed Nov. 1, 2002 and entitled“METHODS FOR FLEXIBLE FLUID DELIVERY AND HOTSPOT COOLING BY MICROCHANNELHEAT SINKS” which is hereby incorporated by reference, as well asco-pending U.S. Provisional Patent Application Ser. No. 60/442,383,filed Jan. 24, 2003 and entitled “OPTIMIZED PLATE FIN HEAT EXCHANGER FORCPU COOLING” which is also hereby incorporated by reference, andco-pending U.S. Provisional Patent Application Ser. No. 60/455,729,filed Mar. 17, 2003 and entitled “MICROCHANNEL HEAT EXCHANGER APPARATUSWITH POROUS CONFIGURATION AND METHOD OF MANUFACTURING THEREOF”, which ishereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for cooling a heatproducing device in general, and specifically, to an interwoven manifoldfor pressure drop reduction in a microchannel heat exchanger.

BACKGROUND OF THE INVENTION

Since their introduction in the early 1980s, microchannel heat sinkshave shown much potential for high heat-flux cooling applications andhave been used in the industry. However, existing microchannels includeconventional parallel channel arrangements which are used are not wellsuited for cooling heat producing devices which have spatially-varyingheat loads. Such heat producing devices have areas which produce moreheat than others. These hotter areas are hereby designated as “hotspots” whereas the areas of the heat source which do not produce as muchheat are hereby termed, “warm spots”.

FIG. 1A illustrates a prior art heat exchanger 10 which is coupled to anelectronic device 99, such as a microprocessor via a thermal interfacematerial 98. As shown in FIG. 1A, fluid generally flows from a singleinlet port 12 and flows along the bottom surface 11 in between theparallel microchannels 14, as shown by the arrows, and exits through theoutlet port 16. Although the heat exchanger 10 cools the electronicdevice 99, the fluid flows from the inlet port 12 to the outlet port 16in a uniform manner. In other words, the fluid flows substantiallyuniformly along the entire bottom surface 11 of the heat exchanger 10and does not supply more fluid to areas in the bottom surface 11 whichcorrespond with hot spots in the device 99. In addition, the temperatureof liquid flowing from the inlet generally increases as it flows alongthe bottom surface 11 of the heat exchanger. Therefore, regions of theheat source 99 which are downstream or near the outlet port 16 are notsupplied with cool fluid, but actually fluid which has already beenheated upstream. In effect, the heated fluid actually propagates theheat across the entire bottom surface 11 of the heat exchanger andregion of the heat source 99, whereby fluid near the outlet port 16 isso hot that it becomes ineffective in cooling heat source. In addition,the heat exchanger 10 having only one inlet 12 and one outlet 16 forcesfluid to travel along the long parallel microchannels 14 in the bottomsurface 11 for the entire length of the heat exchanger 10, therebycreating a large pressure drop.

FIG. 1B illustrates a side view diagram of a prior art multi-level heatexchanger 20. Fluid enters the multi-level heat exchanger 20 through theport 22 and travels downward through multiple jets 28 in the middlelayer 26 to the bottom surface 27 and out port 24. In addition, thefluid traveling along the jets 28 may or may not uniformly flow down tothe bottom surface 27. Nonetheless, although the fluid entering the heatexchanger 20 is spread over the length of the heat exchanger 20, thedesign does not provide more fluid to the hotter areas of the heatexchanger 20 and heat source that are in need of more fluid flowcirculation.

In addition, conventional heat exchangers are made of materials whichhave high thermal resistance in the bottom surface, such that the heatexchanger has a coefficient of thermal expansion which matches that ofthe heat source 99. The high thermal resistance of the heat exchangerthereby does not allow sufficient heat exchange with the heat source 99.To account for the high thermal resistance, larger channelcross-sectional areas are chosen such that more thermal exchange occursbetween the heat exchanger 10 and the heat source 99. In addition, thedimensions of the channels in the heat exchanger are scaled down and thedistance between the channel walls and the hydraulic diameter is madesmaller, the thermal resistance of the heat exchanger is reduced.However, a problem with using narrow microchannels is the increase inpressure drop along the channels. The increase in pressure drop placesextreme demands on a pump driving the fluid through the heat exchanger.In addition, larger microchannel dimensions also cause a larger pressuredrop between the inlet and outlet ports, due to the long distance thatone or two phase fluid must travel. Further, boiling of the fluid in amicrochannel heat exchanger causes a larger pressure drop for a givenflowrate due to the mixing of fluid and vapor as well as theacceleration of the fluid into the vapor phase. Both of these factorsincrease the pressure drop per unit length. The large pressure dropcreated within the current microchannel heat exchangers require largerpumps which can handle higher pressures and thereby are not feasible ina microchannel setting.

What is needed is a microchannel heat exchanger which is configured toachieve proper temperature uniformity in the heat source. What is alsoneeded is a heat exchanger which is configured to achieve properuniformity in light of hot spots in the heat source. What is also neededis a heat exchanger having a relatively high thermal conductivity toadequately perform thermal exchange with the heat source. What isfurther needed is a heat exchanger which is configured to achieve asmall pressure drop between the inlet and outlet fluid ports.

SUMMARY OF THE INVENTION

In one aspect of the invention, a heat exchanger comprises an interfacelayer for cooling a heat source, wherein the interface layer isconfigured to pass fluid therethrough and the interface layer includes athickness within a range of about 0.3 millimeters to about 1.0millimeters, and a manifold layer for circulating fluid to and from theinterface layer, the manifold layer having a first set fingers and asecond set of fingers, wherein the first set of fingers are disposed inparallel with the second set of fingers and arranged to reduce pressuredrop within the heat exchanger. The fluid can be in single phase flowcondition. The fluid can be in two phase flow fluid conditions. At leasta portion of the fluid can undergo a transition between single and twophase flow conditions in the interface layer. A particular finger in thefirst set can be spaced apart by an appropriate dimension from aparticular finger in the second set to minimize the pressure drop in theheat exchanger. Each of the fingers can have the same length and widthdimensions. At least one of the fingers can have a different dimensionthan the remaining fingers. The fingers can be arranged non-periodicallyin at least one dimension in the manifold layer. At least one of thefingers can have at least one varying dimension along a length of themanifold layer. The manifold layer can include more than three and lessthan 10 parallel fingers. The fingers in the first set and second setcan be alternately disposed along a dimension of the manifold layer. Themanifold layer can be configured to cool at least one interface hot spotregion. The heat exchanger can also include at least one first port incommunication with the first set of fingers, wherein fluid enters theheat exchanger through the at least one first port. The heat exchangercan also include at least one second port in communication with thesecond set of fingers, wherein fluid exits the heat exchanger throughthe at least one second port. The manifold layer can be positioned abovethe interface layer, wherein fluid flows downward through the first setof fingers and upward though the second set of fingers. The heatexchanger can also include a first port passage in communication withthe first port and the first set of fingers, the first port passageconfigured to channel fluid from the first port to the first set offingers. The heat exchanger can also include a second port passage incommunication with the second port and the second set of fingers, thesecond port passage configured to channel fluid from the second set offingers to the second port. The interface layer can be integrally formedwith the heat source. The interface layer can be coupled to the heatsource. The heat exchanger can also include an intermediate layer forchanneling fluid to and from one or more predetermined positions in theinterface layer via at least one conduit, the intermediate layerpositioned between the interface layer and the manifold layer. Theintermediate layer can be coupled to the interface layer and themanifold layer. The intermediate layer can be integrally formed with theinterface layer and the manifold layer. The at least one conduit canhave at least one varying dimension along the intermediate layer. Theinterface layer can include a coating thereupon, wherein the coatingprovides an appropriate thermal conductivity of at least 10 W/m-K. Theinterface layer can have a thermal conductivity of at least 100 W/m-K.The heat exchanger can also include a plurality of pillars configured ina predetermined pattern along the interface layer. At least one of theplurality of pillars can have an area dimension within the range of andincluding (10 micron)² and (100 micron)². At least one of the pluralityof pillars can have a height dimension within the range of and including50 microns and 2 millimeters. At least two of the plurality of pillarscan be separate from each other by a spacing dimension within the rangeof and including 10 to 150 microns. The plurality of pillars can includea coating thereupon, wherein the coating has an appropriate thermalconductivity of at least 10 W/m-K. The interface layer can have aroughened surface. The interface layer can include a micro-porousstructure disposed thereon. The porous microstructure can have aporosity within the range of and including 50 to 80 percent. The porousmicrostructure can have an average pore size within the range of andincluding 10 to 200 microns. The porous microstructure can have a heightdimension within the range of and including 0.25 to 2.00 millimeters.The heat exchanger can also include a plurality of microchannelsconfigured in a predetermined pattern along the interface layer. Atleast one of the plurality of microchannels can have an area dimensionwithin the range of and including (10 micron)² and (100 micron)². Atleast one of the plurality of microchannels can have a height dimensionwithin the range of and including 50 microns and 2 millimeters. At leasttwo of the plurality of microchannels can be separate from each other bya spacing dimension within the range of and including 10 to 150 microns.At least one of the plurality of microchannels can have a widthdimension within the range of and including 10 to 100 microns. Theplurality of microchannels can be coupled to the interface layer. Theplurality of microchannels can be integrally formed with the interfacelayer. The plurality of microchannels can be divided into segmentedarrays with at least one groove disposed therebetween, wherein the atleast one groove is aligned with a corresponding finger. The pluralityof microchannels can include a coating thereupon, wherein the coatinghas an appropriate thermal conductivity of at least 10 W/m-K. Anoverhang dimension can be within the range of and including 0 to 15millimeters.

In another aspect of the present invention, a heat exchanger for coolinga heat source comprises a manifold layer including a first set offingers in a first configuration, wherein each finger in the first setchannels fluid at a first temperature, the manifold layer furtherincluding a second set of fingers in a second configuration, whereineach finger in the second set channels fluid at a second temperature,the first set and second set of fingers arranged parallel to each other,and an interface layer including a thickness within a range of about 0.3to 1.0 millimeters, and configured to receive fluid at the firsttemperature at a plurality of first locations, wherein each firstlocation is associated with a corresponding finger in the first set, theinterface layer passing fluid along a plurality of predetermined pathsto a plurality of second locations, wherein each second location isassociated with a corresponding finger in the second set. The fluid canbe in single phase flow conditions. The fluid can be in two phase flowconditions. At least a portion of the fluid can undergo a transitionbetween single and two phase flow conditions in the interface layer. Aparticular finger in the first set can be spaced apart by an appropriatedimension from a particular finger in the second set, wherein theappropriate dimension reduces the pressure drop in the heat exchanger.The heat exchanger can also include at least one first port incommunication with the first set of fingers, wherein fluid enters theheat exchanger through the at least one first port. The heat exchangercan also include at least one second port in communication with thesecond set of fingers, wherein fluid exits the heat exchanger throughthe at least one second port. The manifold layer can be positioned abovethe interface layer, wherein fluid flows downward through the first setof fingers and upward through the second set of fingers. The interfacelayer can be integrally formed with the heat source. The interface layercan be coupled to the heat source. The fingers in the first set can bepositioned in an alternating configuration with the fingers in thesecond set. Each of the fingers can have the same length and widthdimensions. At least one of the fingers can have a different dimensionthan the remaining fingers. The fingers can be arranged non-periodicallyin at least one dimension in the manifold layer. At least one of thefingers can have at least one varying dimension along a length of themanifold layer. The manifold layer can include more than three and lessthan 10 parallel fingers. The heat exchanger can also include a firstport passage in communication with the first port and the first set offingers, the first port passage configured to channel fluid from thefirst port to the first set of fingers. The heat exchanger can alsoinclude a second port passage in communication with the second port andthe second set of fingers, the second port passage configured to channelfluid from the second set of fingers to the second port. The heatexchanger can also include an intermediate layer for channeling fluid toand from one or more predetermined positions in the interface layer viaat least one conduit, the intermediate layer positioned between theinterface layer and the manifold layer. The conduit can be arranged in apredetermined configuration to channel fluid to one or more interfacehot spot regions in the interface layer. The conduit can be arranged ina predetermined configuration to channel fluid from one or moreinterface hot spot regions in the interface layer. The intermediatelayer can be coupled to the interface layer and the manifold layer. Theintermediate layer can be integrally formed with the interface layer andthe manifold layer. The conduit can have at least one varying dimensionin the intermediate layer. The interface layer can include a coatingthereupon, wherein the coating provides an appropriate thermalconductivity of at least 10 W/m-K. The interface layer can have athermal conductivity is at least 10 W/m-K. The heat exchanger can alsoinclude a plurality of pillars configured in a predetermined patternalong the interface layer. At least one of the plurality of pillars canhave an area dimension within the range of and including (10 micron)²and (100 micron)². At least one of the plurality of pillars can have aheight dimension within the range of and including 50 microns and 2millimeters. At least two of the plurality of pillars can be separatefrom each other by a spacing dimension within the range of and including10 to 150 microns. The plurality of pillars can include a coatingthereupon, wherein the coating has an appropriate thermal conductivityof at least 10 W/m-K. The interface layer can have a roughened surface.The interface layer can include a micro-porous structure disposedthereon. The porous microstructure can have a porosity within the rangeof and including 50 to 80 percent. The porous microstructure can have anaverage pore size within the range of and including 10 to 200 microns.The porous microstructure can have a height dimension within the rangeof and including 0.25 to 2.00 millimeters. The heat exchanger can alsoinclude a plurality of microchannels configured in a predeterminedpattern along the interface layer. At least one of the plurality ofmicrochannels can have an area dimension within the range of andincluding (10 micron)² and (100 micron)². At least one of the pluralityof microchannels can have a height dimension within the range of andincluding 50 microns and 2 millimeters. At least two of the plurality ofmicrochannels can be separate from each other by a spacing dimensionwithin the range of and including 10 to 150 microns. At least one of theplurality of microchannels can have a width dimension within the rangeof and including 10 to 100 microns. The microchannels can be coupled tothe interface layer. The microchannels can be integrally formed with theinterface layer. The microchannels can be divided into segments along adimension of the interface layer, at least one groove disposed inbetween the divided microchannel segments. The microchannels can becontinuous along a dimension of the interface layer. The at least onegroove can be aligned with a corresponding finger. The plurality ofmicrochannels can include a coating thereupon, wherein the coating hasan appropriate thermal conductivity of at least 20 W/m-K. An overhangdimension can be within the range of and including 0 to 15 millimeters.

Other features and advantages of the present invention will becomeapparent after reviewing the detailed description of the preferredembodiments set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a side view of a conventional heat exchanger.

FIG. 1B illustrates a top view of the conventional heat exchanger.

FIG. 1C illustrates a side view diagram of a prior art multi-level heatexchanger.

FIG. 2A illustrates a schematic diagram of a closed loop cooling systemincorporating a preferred embodiment of the flexible fluid deliverymicrochannel heat exchanger of the present invention.

FIG. 2B illustrates a schematic diagram of a closed loop cooling systemincorporating an alternative embodiment of the flexible fluid deliverymicrochannel heat exchanger of the present invention.

FIG. 3A illustrates a top view of an alternative manifold layer of theheat exchanger in accordance with the present invention.

FIG. 3B illustrates an exploded view of an alternative heat exchangerwith the alternative manifold layer in accordance with the presentinvention.

FIG. 4 illustrates a perspective view of the preferred interwovenmanifold layer in accordance with the present invention.

FIG. 5 illustrates a top view of the preferred interwoven manifold layerwith interface layer in accordance with the present invention.

FIG. 6A illustrates a cross-sectional view of the preferred interwovenmanifold layer with interface layer of the present invention along linesA-A.

FIG. 6B illustrates a cross-sectional view of the preferred interwovenmanifold layer with interface layer of the present invention along linesB-B.

FIG. 6C illustrates a cross-sectional view of the preferred interwovenmanifold layer with interface layer of the present invention along linesC-C.

FIG. 7A illustrates an exploded view of the preferred interwovenmanifold layer with interface layer of the present invention.

FIG. 7B illustrates a perspective view of an alternative embodiment ofthe interface layer of the present invention.

FIG. 8A illustrates a top view diagram of an alternate manifold layer inaccordance with the present invention.

FIG. 8B illustrates a top view diagram of the interface layer inaccordance with the present invention.

FIG. 8C illustrates a top view diagram of the interface layer inaccordance with the present invention.

FIG. 9A illustrates a side view diagram of the alternative embodiment ofthe three tier heat exchanger in accordance with the present invention.

FIG. 9B illustrates a side view diagram of the alternative embodiment ofthe two tier heat exchanger in accordance with the present invention.

FIG. 10 illustrates a perspective view of the interface layer having amicro-pin array in accordance with the present invention.

FIG. 11 illustrates a cut-away perspective view diagram of the alternateheat exchanger in accordance with the present invention.

FIG. 12 illustrates a side view diagram of the interface layer of theheat exchanger having a coating material applied thereon in accordancewith the present invention.

FIG. 13 illustrates a flow chart of an alternative method ofmanufacturing the heat exchanger in accordance with the presentinvention.

FIG. 14 illustrates a schematic of an alternate embodiment of thepresent invention having two heat exchangers coupled to a heat source.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Generally, the heat exchanger captures thermal energy generated from aheat source by passing fluid through selective areas of the interfacelayer which is preferably coupled to the heat source. In particular, thefluid is directed to specific areas in the interface layer to cool thehot spots and areas around the hot spots to generally create temperatureuniformity across the heat source while maintaining a small pressuredrop within the heat exchanger. As discussed in the differentembodiments below, the heat exchanger utilizes a plurality of apertures,channels and/or fingers in the manifold layer as well as conduits in theintermediate layer to direct and circulate fluid to and from selectedhot spot areas in the interface layer. Alternatively, the heat exchangerincludes several ports which are specifically disposed in predeterminedlocations to directly deliver fluid to and remove fluid from the hotspots to effectively cool the heat source.

It is apparent to one skilled in the art that although the microchannelheat exchanger of the present invention is described and discussed inrelation to flexible fluid delivery for cooling hot spot locations in adevice, the heat exchanger is alternatively used for flexible fluiddelivery for heating a cold spot location in a device. It should also benoted that although the present invention is preferably described as amicrochannel heat exchanger, the present invention can be used in otherapplications and is not limited to the discussion herein.

FIG. 2A illustrates a schematic diagram of a closed loop cooling system30 which includes a preferred flexible fluid delivery microchannel heatexchanger 400 in accordance with the present invention. In addition,FIG. 2B illustrates a schematic diagram of a closed loop cooling system30 which includes an alternative flexible fluid delivery microchannelheat exchanger 200 with multiple ports 108, 109 in accordance with thepresent invention.

As shown in FIG. 2A, the fluid ports 108, 109 are coupled to fluid lines38 which are coupled to a pump 32 and heat condensor 30. The pump 32pumps and circulates fluid within the closed loop 30. It is preferredthat one fluid port 108 is used to supply fluid to the heat exchanger100. In addition, it is preferred that one fluid port 109 is used toremove fluid from the heat exchanger 100. Preferably a uniform, constantamount of fluid flow enters and exits the heat exchanger 100 via therespective fluid ports 108, 109. Alternatively, different amounts offluid flow enter and exit through the inlet and outlet port(s) 108, 109at a given time. Alternatively, as shown in FIG. 2B, one pump providesfluid to several designated inlet ports 108. Alternatively, multiplepumps (not shown), provide fluid to their respective inlet and outletports 108, 109. In addition, the dynamic sensing and control module 34is alternatively employed in the system to variate and dynamicallycontrol the amount and flow rate of fluid entering and exiting thepreferred or alternative heat exchanger in response to varying hot spotsor changes in the amount of heat in a hot spot location as well as thelocations of the hot spots.

The preferred embodiment is a three level heat exchanger 400 whichincludes an interface layer 402, at least one intermediate layer 404 andat least one manifold layer 406. The preferred manifold layer 402 andthe preferred interface layer 402 are shown in FIG. 7 and theintermediate layer 104 is shown in FIG. 3B. Alternatively, as discussedbelow, the heat exchanger 400 is a two level apparatus which includesthe interface layer 402 and the manifold layer 406, as shown in FIG. 7.As shown in FIGS. 2A and 2B, the heat exchanger 400 is coupled to a heatsource 99, such as an electronic device, including, but not limited to amicrochip and integrated circuit, whereby a thermal interface material98 is preferably disposed between the heat source 99 and the heatexchanger 100. Alternatively, the heat exchanger 400 is directly coupledto the surface of the heat source 99. It is also apparent to one skilledin the art that the heat exchanger 400 is alternatively integrallyformed into the heat source 99, whereby the heat exchanger 400 and theheat source 99 are formed as one piece. Thus, the interface layer 102 isintegrally disposed with the heat source 99 and is formed as one piecewith the heat source.

It is preferred that the heat exchanger 400 of the present invention isconfigured to be directly or indirectly in contact with the heat source99 which is rectangular in shape, as shown in the figures. However, itis apparent to one skilled in the art that the heat exchanger 400 canhave any other shape conforming with the shape of the heat source 99.For example, the heat exchanger of the present invention can beconfigured to have an outer semicircular shape which allows the heatexchanger (not shown) to be in direct or indirect contact with acorresponding semicircular shaped heat source (not shown). In addition,it is preferred that the heat exchanger 400 is slightly larger indimension than the heat source within the range of and including 0.5-5.0millimeters.

FIG. 3A illustrates a top view of the alternate manifold layer 106 ofthe present invention. In particular, as shown in FIG. 3B, the manifoldlayer 106 includes four sides as well as a top surface 130 and a bottomsurface 132. However, the top surface 130 is removed in FIG. 3A toadequately illustrate and describe the workings of the manifold layer106. As shown in FIG. 3A, the manifold layer 106 has a series ofchannels or passages 1116, 118, 120, 122 as well as ports 108, 109formed therein. The fingers 1118, 120 extend completely through the bodyof the manifold layer 106 in the Z-direction as shown in FIG. 3B.Alternatively, the fingers 118 and 120 extend partially through themanifold layer 106 in the Z-direction and have apertures as shown inFIG. 3A. In addition, passages 116 and 122 extend partially through themanifold layer 106. The remaining areas between the inlet and outletpassages 116, 120, designated as 107, extend from the top surface 130 tothe bottom surface 132 and form the body of the manifold layer 106.

As shown in FIG. 3A, the fluid enters manifold layer 106 via the inletport 108 and flows along the inlet channel 116 to several fingers 118which branch out from the channel 116 in several directions in the Xand/or Y directions to apply fluid to selected regions in the interfacelayer 102. The fingers 118 are arranged in different predetermineddirections to deliver fluid to the locations in the interface layer 102corresponding to the areas at or near the hot spots in the heat source.These locations in the interface layer 102 are hereinafter referred toas interface hot spot regions. The fingers are configured to coolstationary as well as temporally varying interface hot spot regions. Asshown in FIG. 3A, the channels 116, 122 and fingers 118, 120 aredisposed in the X and/or Y directions in the manifold layer 106. Thus,the various directions of the channels 116, 122 and fingers 1118, 120allow delivery of fluid to cool hot spots in the heat source 99 and/orminimize pressure drop within the heat exchanger 100. Alternatively,channels 116, 122 and fingers 1118, 120 are periodically disposed in themanifold layer 106 and exhibit a pattern, as in the preferredembodiment.

The arrangement as well as the dimensions of the fingers 118, 120 aredetermined in light of the hot spots in the heat source 99 that aredesired to be cooled. The locations of the hot spots as well as theamount of heat produced near or at each hot spot are used to configurethe manifold layer 106 such that the fingers 118, 120 are placed aboveor proximal to the interface hot spot regions in the interface layer102. The manifold layer 106 preferably allows one phase and/or two-phasefluid to circulate to the interface layer 102 without allowing asubstantial pressure drop from occurring within the heat exchanger 100and the system 30 (FIG. 2A). The fluid delivery to the interface hotspot regions creates a uniform temperature at the interface hot spotregion as well as areas in the heat source adjacent to the interface hotspot regions.

The dimensions as well as the number of channels 116 and fingers 118depend on a number of factors. In one embodiment, the inlet and outletfingers 118, 120 have the same width dimensions. Alternatively, theinlet and outlet fingers 118, 120 have different width dimensions. Thewidth dimensions of the fingers 118, 120 are preferably within the rangeof and including 0.25-0.50 millimeters. In one embodiment, the inlet andoutlet fingers 118, 120 have the same length and depth dimensions.Alternatively, the inlet and outlet fingers 118, 120 have differentlength and depth dimensions. In another embodiment, the inlet and outletfingers 118, 120 have varying width dimensions along the length of thefingers. The length dimensions of the inlet and outlet fingers 118, 120are within the range of and including 0.5 millimeters to three times thesize of the heat source length. In addition, the fingers 118, 120 have aheight or depth dimension within the range and including 0.25-0.50millimeters. In addition, less than 10 or more than 30 fingers percentimeter are disposed in the manifold layer 106. However, it isapparent to one skilled in the art that between 10 and 30 fingers percentimeter in the manifold layer is alternatively contemplated.

It is contemplated within the present invention to tailor the geometriesof the fingers 118, 120 and channels 116, 122 to be in non-periodicarrangement to aid in optimizing hot spot cooling of the heat source. Inorder to achieve a uniform temperature across the heat source 99, thespatial distribution of the heat transfer to the fluid is matched withthe spatial distribution of the heat generation. As the fluid flowsalong the interface layer through the microchannels 110, its temperatureincreases and as it begins to transform to vapor under two-phaseconditions. Thus, the fluid undergoes a significant expansion whichresults in a large increase in velocity. Generally, the efficiency ofthe heat transfer from the interface layer to the fluid is improved forhigh velocity flow. Therefore, it is possible to tailor the efficiencyof the heat transfer to the fluid by adjusting the cross-sectionaldimensions of the fluid delivery and removal fingers 118, 120 andchannels 116, 122 in the heat exchanger 100.

For example, a particular finger can be designed for a heat source wherethere is higher heat generation near the inlet. In addition, it may beadvantageous to design a larger cross section for the regions of thefingers 118, 120 and channels 116, 122 where a mixture of fluid andvapor is expected. Although not shown, a finger can be designed to startout with a small cross sectional area at the inlet to cause highvelocity flow of fluid. The particular finger or channel can also beconfigured to expand to a larger cross-section at a downstream outlet tocause a lower velocity flow. This design of the finger or channel allowsthe heat exchanger to minimize pressure drop and optimize hot spotcooling in areas where the fluid increases in volume, acceleration andvelocity due to transformation from liquid to vapor in two-phase flow.

In addition, the fingers 118, 120 and channels 116, 122 can be designedto widen and then narrow again along their length to increase thevelocity of the fluid at different places in the microchannel heatexchanger 100. Alternatively, it may be appropriate to vary the fingerand channel dimensions from large to small and back again many timesover in order to tailor the heat transfer efficiency to the expectedheat dissipation distribution across the heat source 99. It should benoted that the above discussion of the varying dimensions of the fingersand channels also apply to the other embodiments discussed and is notlimited to this embodiment.

Alternatively, as shown in FIG. 3A, the manifold layer 106 includes oneor more apertures 119 in the inlet fingers 118. In the three tier heatexchanger 100, the fluid flowing along the fingers 118 flows down theapertures 119 to the intermediate layer 104. Alternatively, in thetwo-tier heat exchanger 100, the fluid flowing along the fingers 118flows down the apertures 119 directly to the interface layer 102. Inaddition, as shown in FIG. 3A. the manifold layer 106 includes apertures121 in the outlet fingers 120. In the three tier heat exchanger 100, thefluid flowing from the intermediate layer 104 flows up the apertures 121into the outlet fingers 120. Alternatively, in the two-tier heatexchanger 100, the fluid flowing from the interface layer 102 flowsdirectly up the apertures 121 into the outlet fingers 120.

In the embodiment shown in FIG. 3A, the inlet and outlet fingers 1118,120 are open channels which do not have apertures. The bottom surface103 of the manifold layer 106 abuts against the top surface of theintermediate layer 104 in the three tier exchanger 100 or abuts againstthe interface layer 102 in the two tier exchanger. Thus, in thethree-tier heat exchanger 100, fluid flows freely to and from theintermediate layer 104 and the manifold layer 106. The fluid is directedto and from the appropriate interface hot spot region by conduits 105the intermediate layer 104. It is apparent to one skilled in the artthat the conduits 105 are directly aligned with the fingers, asdescribed below or positioned elsewhere in the three tier system.

FIG. 3B illustrates an exploded view of the three tier heat exchanger100 with the alternate manifold layer in accordance with the presentinvention. Alternatively, the heat exchanger 100 is a two layerstructure which includes the manifold layer 106 and the interface layer102, whereby fluid passes directly between the manifold layer 106 andinterface layer 102 without passing through the intermediate layer 104.It is apparent to one skilled in the art that the configuration of themanifold, intermediate and interface layers are shown for exemplarypurposes and is thereby not limited to the configuration shown.

As shown in FIG. 3B, the intermediate layer 104 includes a plurality ofconduits 105 which extend therethrough. The inflow conduits 105 directfluid entering from the manifold layer 106 to the designated interfacehot spot regions in the interface layer 102. Similarly, the apertures105 also channel fluid flow from the interface layer 102 to the exitfluid port(s) 109. Thus, the intermediate layer 104 also provides fluiddelivery from the interface layer 102 to the exit fluid port 109 wherethe exit fluid port 108 is in communication with the manifold layer 106.

The conduits 105 are positioned in the interface layer 104 in apredetermined pattern based on a number of factors including, but notlimited to, the locations of the interface hot spot regions, the amountof fluid flow needed in the interface hot spot region to adequately coolthe heat source 99 and the temperature of the fluid. The conduits have awidth dimension of 100 microns, although other width dimensions arecontemplated up to several millimeters. In addition, the conduits 105have other dimensions dependent on at least the above mentioned factors.It is apparent to one skilled in the art that each conduit 105 in theintermediate layer 104 has a same shape and/or dimension, although it isnot necessary. For instance, like the fingers described above, theconduits alternatively have a varying length and/or width dimension.Additionally, the conduits 105 may have a constant depth or heightdimension through the intermediate layer 104. Alternatively, theconduits 105 have a varying depth dimension, such as a trapezoidal or anozzle-shape, through the intermediate layer 104. Although thehorizontal shape of the conduits 105 are shown to be rectangular in FIG.2C, the conduits 105 alternatively have any other shape including, butnot limited to, circular (FIG. 3A), curved and elliptical.Alternatively, one or more of the conduits 105 are shaped and contourwith a portion of or all of the finger or fingers above.

The intermediate layer 104 is horizontally positioned within the heatexchanger 100 with the conduits 105 positioned vertically.Alternatively, the intermediate layer 104 is positioned in any otherdirection within the heat exchanger 100 including, but not limited to,diagonal and curved forms. Alternatively, the conduits 105 arepositioned within the intermediate layer 104 in a horizontally,diagonally, curved or any other direction. In addition, the intermediatelayer 104 extends horizontally along the entire length of the heatexchanger 100, whereby the intermediate layer 104 completely separatesthe interface layer 102 from the manifold layer 106 to force the fluidto be channeled through the conduits 105. Alternatively, a portion ofthe heat exchanger 100 does not include the intermediate layer 104between the manifold layer 106 and the interface layer 102, wherebyfluid is free to flow therebetween. Further, the intermediate layer 104alternatively extends vertically between the manifold layer 106 and theinterface layer 102 to form separate, distinct intermediate layerregions. Alternatively, the intermediate layer 104 does not fully extendfrom the manifold layer 106 to interface layer 102.

It is preferred that the heat exchanger 100 of the present invention islarger in width than the heat source 99. In the case where the heatexchanger 100 is larger than the heat source 99, an overhang dimensionexists. The overhang dimension is the farthest distance between oneouter wall of the heat source 99 and the interior fluid channel wall ofthe heat exchanger 100, such as the inner wall of the inlet port 408(FIG. 4). In the preferred embodiment, the overhang dimension is withinthe range of and including 0 to 5 millimeters for single phase and 0 to15 millimeters for two phase fluid.

FIG. 10 illustrates a perspective view of one embodiment of an interfacelayer 202′ in accordance with the present invention. As shown in FIG.10, the interface layer 202′ includes a series of pillars 203 whichextend upwards from a top surface of the interface layer 202′. Inaddition, FIG. 10 illustrates a microporous structure 213 disposed onthe top surface of the interface layer 202′. It is apparent that theinterface layer 202′ can include only the microporous structure 213 aswell as a combination of the microporous structure with any otherinterface layer feature (e.g. microchannels, pillars, etc.). Inaddition, the interface layer 202′ of the present invention preferablyhas a thickness dimension within the range of and including 0.3 to 0.7millimeters for single phase fluid and 0.3 to 1.0 millimeters for twophase fluid.

In the embodiment of the heat exchanger which utilizes a microporousstructure 213 disposed upon the interface layer 202′, the microporousstructure 213 has an average pore size within the range of and including10 to 200 microns for single phase as well as two phase fluid. Inaddition, the microporous structure 213 has a porosity within the rangeand including 50 to 80 percent for single phase as well as two phasefluid. The height of the microporous structure 213 is within the rangeof and including 0.25 to 2.00 millimeters for single phase as well astwo phase fluid.

In the embodiment which utilizes pillars and/or microchannels along theinterface layer 202′, the interface layer 202′ of the present inventionhas a thickness dimension in the range of and including 0.3 to 0.7millimeters for single phase fluid and 0.3 to 1.0 millimeters for twophase fluid. In addition, the area of at least one pillar, ormicrochannel, is in the range of and including (10 micron)² and (100micron)² for single phase as well as two phase fluid. In addition, thearea of the separation distance between at least two of the pillarsand/or microchannels is in the range of and including 10 microns to 150microns for single phase as well as two phase fluid. The width dimensionof the microchannels are in the range of and including 10 to 100 micronsfor single phase as well as two phase fluid. The height dimension of themicrochannels and/or pillars is within the range of and including 50 to800 microns for single phase fluid and 50 microns to 2 millimeters fortwo phase fluid. It is contemplated by one skilled in the art that otherdimension are alternatively contemplated.

FIG. 3B illustrates a perspective view of the interface layer 102 inaccordance with the present invention. As shown in FIG. 3B, theinterface layer 102 includes a bottom surface 103 and a plurality ofmicrochannel walls 110, whereby the area in between the microchannelwalls 110 channels or directs fluid along a fluid flow path. The bottomsurface 103 is flat and has a high thermal conductivity to allowsufficient heat transfer from the heat source 99. Alternatively, thebottom surface 103 includes troughs and/or crests designed to collect orrepel fluid from a particular location. The microchannel walls 110 areconfigured in a parallel configuration, as shown in FIG. 3B, wherebyfluid preferably flows between the microchannel walls 110 along a fluidpath. Alternatively, the microchannel walls 110 have non-parallelconfigurations.

It is apparent to one skilled in the art that the microchannel walls 110are alternatively configured in any other appropriate configurationdepending on the factors discussed above. For instance, the interfacelayer 102 alternatively has grooves in between sections of microchannelwalls 110, as shown in FIG. 8C. In addition, the microchannel walls 110have dimensions which minimize the pressure drop or differential withinthe interface layer 102. It is also apparent that any other features,besides microchannel walls 110 are also contemplated, including, but notlimited to, pillars (FIG. 10), roughed surfaces, and a micro-porousstructure, such as sintered metal and silicon foam (FIG. 10). However,for exemplary purposes, the parallel microchannel walls 110 shown inFIG. 3B is used to describe the interface layer 102 in the presentinvention.

The microchannel walls 110 allow the fluid to undergo thermal exchangealong the selected hot spot locations of the interface hot spot regionto cool the heat source 99 in that location. The microchannel walls 110have a width dimension within the range of 10-100 microns and a heightdimension within the range of 50 microns to two millimeters, dependingon the power of the heat source 99. The microchannel walls 110 have alength dimension which ranges between 100 microns and severalcentimeters, depending on the dimensions of the heat source, as well asthe size of the hot spots and the heat flux density from the heatsource. Alternatively, any other microchannel wall dimensions arecontemplated. The microchannel walls 110 are spaced apart by aseparation dimension range of 50-500 microns, depending on the power ofthe heat source 99, although any other separation dimension range iscontemplated.

Referring back to the assembly in FIG. 3B, the top surface of themanifold layer 106 is cut away to illustrate the channels 116, 122 andfingers 118, 120 within the body of the manifold layer 106. Thelocations in the heat source 99 that produce more heat are herebydesignated as hot spots, whereby the locations in the heat source 99which produce less heat are hereby designated as warm spots. As shown inFIG. 3B, the heat source 99 is shown to have a hot spot region, namelyat location A, and a warm spot region, namely at location B. The areasof the interface layer 102 which abut the hot and warm spots areaccordingly designated interface hot spot regions. As shown in FIG. 3B,the interface layer 102 includes interface hot spot region A, which ispositioned above location A and interface hot spot region B, which ispositioned above location B.

As shown in FIGS. 3A and 3B, fluid initially enters the heat exchanger100 through one inlet port 108. The fluid then preferably flows to oneinlet channel 116. Alternatively, the heat exchanger 100 includes morethan one inlet channel 116. As shown in FIGS. 3A and 3B, fluid flowingalong the inlet channel 116 from the inlet port 108 initially branchesout to finger 118D. In addition, the fluid which continues along therest of the inlet channel 116 flows to individual fingers 1181B and 118Cand so on.

In FIG. 3B, fluid is supplied to interface hot spot region A by flowingto the finger 118A, whereby fluid flows down through finger 118A to theintermediate layer 104. The fluid then flows through the inlet conduit105A positioned below the finger 118A to the interface layer 102,whereby the fluid undergoes thermal exchange with the heat source 99.The fluid travels along the microchannels 110 as shown in FIG. 3B,although the fluid may travel in any other direction along the interfacelayer 102. The heated liquid then travels upward through the conduit105B to the outlet finger 120A. Similarly, fluid flows down in theZ-direction through fingers 118E and 118F to the intermediate layer 104.The fluid then flows through the inlet conduit 105C down in theZ-direction to the interface layer 102. The heated fluid then travelsupward in the Z-direction from the interface layer 102 through theoutlet conduit 105D to the outlet fingers 120E and 120F. The heatexchanger 100 removes the heated fluid in the manifold layer 106 via theoutlet fingers 120, whereby the outlet fingers 120 are in communicationwith the outlet channel 122. The outlet channel 122 allows fluid to flowout of the heat exchanger through one outlet port 109.

In one embodiment, the inflow and outflow conduits 105 are positioneddirectly or nearly directly above the appropriate interface hot spotregions to directly apply fluid to hot spots in the heat source 99. Inaddition, each outlet finger 120 is configured to be positioned closestto a respective inlet finger 119 for a particular interface hot spotregion to minimize pressure drop therebetween. Thus, fluid enters theinterface layer 102 via the inlet finger 118A and travels the leastamount of distance along the bottom surface 103 of the interface layer102 before it exits the interface layer 102 to the outlet finger 120A.It is apparent that the amount of distance which the fluid travels alongthe bottom surface 103 adequately removes heat generated from the heatsource 99 without generating an unnecessary amount of pressure drop. Inaddition, as shown in FIGS. 3A and 3B, the corners in the fingers 118,120 are curved to reduce pressure drop of the fluid flowing along thefingers 118.

It is apparent to one skilled in the art that the configuration of themanifold layer 106 shown in FIGS. 3A and 3B is only for exemplarypurposes. The configuration of the channels 116 and fingers 118 in themanifold layer 106 depend on a number of factors, including but notlimited to, the locations of the interface hot spot regions, amount offlow to and from the interface hot spot regions as well as the amount ofheat produced by the heat source in the interface hot spot regions. Forinstance, the preferred configuration of the manifold layer 106 includesan interdigitated pattern of parallel inlet and outlet fingers that arearranged along the width of the manifold layer, as shown in FIGS. 4-7Aand discussed below. Nonetheless, any other configuration of channels116 and fingers 118 is contemplated.

FIG. 4 illustrates a perspective view of the preferred manifold layer406 in accordance with the heat exchanger of the present invention. Themanifold layer 406 in FIG. 4 preferably includes a plurality ofinterwoven or inter-digitated parallel fluid fingers 411, 412 whichallow one phase and/or two-phase fluid to circulate to the interfacelayer 402 without allowing a substantial pressure drop from occurringwithin the heat exchanger 400 and the system 30 (FIG. 2A). As shown inFIG. 8, the inlet fingers 411 are arranged alternately with the outletfingers 412. However, it is contemplated by one skilled in the art thata certain number of inlet or outlet fingers can be arranged adjacent toone another and is thereby not limited to the alternating configurationshown in FIG. 4. In addition, the fingers are alternatively designedsuch that a parallel finger branches off from or is linked to anotherparallel finger. Thus, it is possible to have many more inlet fingersthan outlet fingers and vice versa.

The inlet fingers or passages 411 supply the fluid entering the heatexchanger to the interface layer 402, and the outlet fingers or passages412 remove the fluid from the interface layer 402 which then exits theheat exchanger 400. The preferred configuration of the manifold layer406 allows the fluid to enter the interface layer 402 and travel a veryshort distance in the interface layer 402 before it enters the outletpassage 412. The substantial decrease in the length that the fluidtravels along the interface layer 402 substantially decreases thepressure drop in the heat exchanger 400 and the system 30 (FIG. 2A).

As shown in FIGS. 4-5, the preferred manifold layer 406 includes apassage 414 which is in communication with two inlet passages 411 andprovides fluid thereto. As shown in FIGS. 8-9 the manifold layer 406includes three outlet passages 412 which are in communication withpassage 418. Preferably the passages 414 in the manifold layer 406 havea flat bottom surface which channels the fluid to the fingers 411, 412.Alternatively, the passage 414 has a slight slope which aids inchanneling the fluid to selected fluid passages 411. Alternatively, theinlet passage 414 includes one or more apertures in its bottom surfacewhich allows a portion of the fluid to flow down to the interface layer402. Similarly, the passage 418 in the manifold layer has a flat bottomsurface which contains the fluid and channels the fluid to the port 408.Alternatively, the passage 418 has a slight slope which aids inchanneling the fluid to selected outlet ports 408. In addition, thepassages 414, 418 have a dimension width of approximately 2 millimeters,although any other width dimensions are alternatively contemplated.

The passages 414, 418 are in communication with ports 408, 409 wherebythe ports are coupled to the fluid lines 38 in the system 30 (FIG. 2A).The manifold layer 406 preferably includes horizontally configured fluidports 408, 409. Alternatively, the manifold layer 406 includesvertically and/or diagonally configured fluid ports 408, 409, asdiscussed below, although not shown in FIG. 4-7. Alternatively, themanifold layer 406 does not include passage 414. Thus, fluid is directlysupplied to the fingers 411 from the ports 408. Again, the manifoldlayer 411 alternatively does not include passage 418, whereby fluid inthe fingers 412 directly flows out of the heat exchanger 400 throughports 408. It is apparent that although two ports 408 are shown incommunication with the passages 414, 418, any other number of ports arealternatively utilized.

The inlet passages 411 preferably have dimensions which allow fluid totravel to the interface layer without generating a large pressure dropalong the passages 411 and the system 30 (FIG. 2A). The inlet passages411 preferably have a width dimension in the range of and including0.25-5.00 millimeters, although any other width dimensions arealternatively contemplated. In addition, the inlet passages 411preferably have a length dimension in the range of and including 0.5millimeters to three times the length of the heat source. Alternatively,other length dimensions are contemplated. In addition, as stated above,the inlet passages 411 extend down to or slightly above the height ofthe microchannels 410 such that the fluid is channeled directly to themicrochannels 410. The inlet passages 411 preferably have a heightdimension in the range of and including 0.25-5.00 millimeters. It isapparent to one skilled in the art that the passages 411 do not extenddown to the microchannels 410 and that any other height dimensions arealternatively contemplated. It is apparent to one skilled in the artthat although the inlet passages 411 have the same dimensions, it iscontemplated that the inlet passages 411 alternatively have differentdimensions. In addition, the inlet passages 411 alternatively havevarying widths, cross sectional dimensions and/or distances betweenadjacent fingers. varying dimensions. In particular, the passage 411 hasareas with a larger width or depths as well as areas with narrowerwidths and depths along its length. The varied dimensions allow morefluid to be delivered to predetermined interface hot spot regions in theinterface layer 402 through wider portions while restricting flow towarm spot interface hot spot regions through the narrow portions.

In addition, the outlet passages 412 preferably have dimensions whichallow fluid to travel to the interface layer without generating a largepressure drop along the passages 412 as well as the system 30 (FIG. 2A).The outlet passages 412 preferably have a width dimension in the rangeof and including 0.25-5.00 millimeters, although any other widthdimensions are alternatively contemplated. In addition, the outletpassages 412 preferably have a length dimension in the range of andincluding 0.5 millimeters to three times the length of the heat source.In addition, the outlet passages 412 extend down to the height of themicrochannels 410 such that the fluid easily flows upward in the outletpassages 412 after horizontally flowing along the microchannels 410. Theinlet passages 411 preferably have a height dimension in the range ofand including 0.25-5.00 millimeters, although any other heightdimensions are alternatively contemplated. It is apparent to one skilledin the art that although outlet passages 412 have the same dimensions,it is contemplated that the outlet passages 412 alternatively havedifferent dimensions. Again, the inlet passage 412 alternatively havevarying widths, cross sectional dimensions and/or distances betweenadjacent fingers.

The inlet and outlet passages 411, 412 are preferably segmented anddistinct from one another, as shown in FIGS. 4 and 5, whereby fluidamong the passages do not mix together. In particular, as shown in FIG.8, two outlet passages are located along the outside edges of themanifold layer 406, and one outlet passage 412 is located in the middleof the manifold layer 406. In addition, two inlet passages 411 areconfigured on adjacent sides of the middle outlet passage 412. Thisparticular configuration causes fluid entering the interface layer 402to travel the a short distance in the interface layer 402 before itflows out of the interface layer 402 through the outlet passage 412.However, it is apparent to one skilled in the art that the inletpassages and outlet passages may be positioned in any other appropriateconfiguration and is thereby not limited to the configuration shown anddescribed in the present disclosure. The number of inlet and outletfingers 411, 412 are more than three within the manifold layer 406 butless than 10 per centimeter across the manifold layer 406. It is alsoapparent to one skilled in the art that any other number of inletpassages and outlet passages may be used and thereby is not limited tothe number shown and described in the present disclosure.

Preferably, the manifold layer 406 is coupled to the intermediate layer(not shown), whereby the intermediate layer (not shown) is coupled tothe interface layer 402 to form a three-tier heat exchanger 400. Theintermediate layer discussed herein is referred to above in theembodiment shown in FIG. 3B. The manifold layer 406 is alternativelycoupled to the interface layer 402 and positioned above the interfacelayer 402 to form a two-tier heat exchanger 400, as shown in FIG. 7A.FIGS. 6A-6C illustrate cross-sectional schematics of the preferredmanifold layer 406 coupled to the interface layer 402 in the two tierheat exchanger. Specifically, FIG. 6A illustrates the cross section ofthe heat exchanger 400 along line A-A in FIG. 5. In addition, FIG. 6Billustrates the cross section of the heat exchanger 400 along line B-Band FIG. 6C illustrates the cross section of the heat exchanger 400along line C-C in FIG. 5. As stated above, the inlet and outlet passages411, 412 extend from the top surface to the bottom surface of themanifold layer 406. When the manifold layer 406 and the interface layer402 are coupled to one another, the inlet and outlet passages 411, 412are at or slightly above the height of the microchannels 410 in theinterface layer 402. This configuration causes the fluid from the inletpassages 411 to easily flow from the passages 411 through themicrochannels 410. In addition, this configuration causes fluid flowingthrough the microchannels to easily flow upward through the outletpassages 412 after flowing through the microchannels 410.

In the preferred embodiment, the intermediate layer 104 (FIG. 3B) ispositioned between the manifold layer 406 and the interface layer 402,although not shown in the figures. The intermediate layer 104 (FIG. 3B)channels fluid flow to designated interface hot spot regions in theinterface layer 402. In addition, the intermediate layer 104 (FIG. 3B)is preferably utilized to provide a uniform flow of fluid entering theinterface layer 402. Also, the intermediate layer 104 is preferablyutilized to provide fluid to interface hot spot regions in the interfacelayer 402 to adequately cool hot spots and create temperature uniformityin the heat source 99. Although, the inlet and outlet passages 411, 412are preferably positioned near or above hot spots in the heat source 99to adequately cool the hot spots, although it is not necessary.

FIG. 7A illustrates an exploded view of the alternate manifold layer 406with the an alternative interface layer 102 of the present invention.Preferably, the interface layer 102 includes continuous arrangements ofmicrochannel walls 110, as shown in FIG. 3B. In general operation,similar to the preferred manifold layer 106 shown in FIG. 3B, fluidenters the manifold layer 406 at fluid port 408 and travels through thepassage 414 and towards the fluid fingers or passages 411. The fluidenters the opening of the inlet fingers 411 and preferably flows thelength of the fingers 411 in the X-direction, as shown by the arrows. Inaddition, the fluid flows downward in the Z-direction to the interfacelayer 402 which is positioned below to the manifold layer 406. As shownin FIG. 7A, the fluid in the interface layer 402 traverses along thebottom surface in the X and Y directions of the interface layer 402 andperforms thermal exchange with the heat source 99. The heated fluidexits the interface layer 402 by preferably flowing upward in theZ-direction via the outlet fingers 412, whereby the outlet fingers 412channel the heated fluid to the passage 418 in the manifold layer 406 inthe X-direction. The fluid then flows along the passage 418 and exitsthe heat exchanger by flowing out through the port 409.

The interface layer, as shown in FIG. 7A, includes a series of grooves416 disposed in between sets of microchannels 410 which aid inchanneling fluid to and from the passages 411, 412. In particular, thegrooves 416A are located directly beneath the inlet passages 411 of thealternate manifold layer 406, whereby fluid entering the interface layer402 via the inlet passages 411 is directly channeled to themicrochannels adjacent to the groove 416A. Thus, the grooves 416A allowfluid to be directly channeled into specific designated flow paths fromthe inlet passages 411, as shown in FIG. 5. Similarly, the interfacelayer 402 includes grooves 416B which are located directly beneath theoutlet passages 412 in the Z-direction. Thus, fluid flowing horizontallyalong the microchannels 410 toward the outlet passages are channeledhorizontally to the grooves 416B and vertically to the outlet passage412 above the grooves 416B.

FIG. 6A illustrates the cross section of the heat exchanger 400 withmanifold layer 406 and interface layer 402. In particular, FIG. 6A showsthe inlet passages 411 interwoven with the outlet passages 412, wherebyfluid flows down the inlet passages 411 and up the outlet passages 412.In addition, as shown in FIG. 6A, the fluid flows horizontally throughthe microchannel walls 410 which are disposed between the inlet passagesand outlet passages and separated by the microchannels 410.Alternatively, the microchannel walls are continuous (FIG. 3B) and arenot separated by the grooves. As shown in FIG. 6A, either or both of theinlet and outlet passages 411, 412 preferably have a curved surface 420at their ends at the location near the grooves 416. The curved surface420 directs fluid flowing down the passage 411 towards the microchannels410 which are located adjacent to the passage 411. Thus, fluid enteringthe interface layer 102 is more easily directed toward the microchannels410 instead of flowing directly to the groove 416A. Similarly, thecurved surface 420 in the outlet passages 412 assists in directing fluidfrom the microchannels 410 to the outer passage 412.

In an alternative embodiment, as shown in FIG. 7B, the interface layer402′ includes the inlet passages 411′ and outlet passages 412′ discussedabove with respect to the manifold layer 406 (FIGS. 8-9). In thealternative embodiment, the fluid is supplied directly to the interfacelayer 402′ from the port 408′. The fluid flows along the passage 414′towards the inlet passages 411′. The fluid then traverses laterallyalong the sets of microchannels 410′ and undergoes heat exchange withthe heat source (not shown) and flows to the outlet passages 412′. Thefluid then flows along the outlet passages 412′ to passage 418′, wherebythe fluid exits the interface layer 402′ by via the port 409′. The ports408′, 409′ are configured in the interface layer 402′ and arealternatively configured in the manifold layer 406 (FIG. 7A).

It is apparent to one skilled in the art that although all of the heatexchangers in the present application are shown to operate horizontally,the heat exchanger alternatively operates in a vertical position. Whileoperating in the vertical position, the heat exchangers arealternatively configured such that each inlet passage is located abovean adjacent outlet passage. Therefore, fluid enters the interface layerthrough the inlet passages and is naturally channeled to an outletpassage. It is also apparent that any other configuration of themanifold layer and interface layer is alternatively used to allow theheat exchanger to operate in a vertical position.

FIGS. 8A-8C illustrate top view diagrams of another alternate embodimentof the heat exchanger in accordance with the present invention. Inparticular, FIG. 8A illustrates a top view diagram of an alternatemanifold layer 206 in accordance with the present invention. FIGS. 8Band 8C illustrate a top view of an intermediate layer 204 and interfacelayer 202. In addition, FIG. 9A illustrates a three tier heat exchangerutilizing the alternate manifold layer 206, whereas FIG. 9B illustratesa two-tier heat exchanger utilizing the alternate manifold layer 206.

As shown in FIGS. 8A and 9A, the manifold layer 206 includes a pluralityof fluid ports 208 configured horizontally and vertically.Alternatively, the fluid ports 208 are positioned diagonally or in anyother direction with respect to the manifold layer 206. The fluid ports208 are placed in selected locations in the manifold layer 206 toeffectively deliver fluid to the predetermined interface hot spotregions in the heat exchanger 200. The multiple fluid ports 208 providea significant advantage, because fluid can be directly delivered from afluid port to a particular interface hot spot region withoutsignificantly adding to the pressure drop to the heat exchanger 200. Inaddition, the fluid ports 208 are also positioned in the manifold layer206 to allow fluid in the interface hot spot regions to travel the leastamount of distance to the exit port 208 such that the fluid achievestemperature uniformity while maintaining a minimal pressure drop betweenthe inlet and outlet ports 208. Additionally, the use of the manifoldlayer 206 aids in stabilizing two phase flow within the heat exchanger200 while evenly distributing uniform flow across the interface layer202. It should be noted that more than one manifold layer 206 isalternatively included in the heat exchanger 200, whereby one manifoldlayer 206 routes the fluid into and out-of the heat exchanger 200 andanother manifold layer (not shown) controls the rate of fluidcirculation to the heat exchanger 200. Alternatively, all of theplurality of manifold layers 206 circulate fluid to selectedcorresponding interface hot spot regions in the interface layer 202.

The alternate manifold layer 206 has lateral dimensions which closelymatch the dimensions of the interface layer 202. In addition, themanifold layer 206 has the same dimensions of the heat source 99.Alternatively, the manifold layer 206 is larger than the heat source 99.The vertical dimensions of the manifold layer 206 are within the rangeof 0.1 and 10 millimeters. In addition, the apertures in the manifoldlayer 206 which receive the fluid ports 208 are within the range between1 millimeter and the entire width or length of the heat source 99.

FIG. 11 illustrates a broken-perspective view of a three tier heatexchanger 200 having the alternate manifold layer 200 in accordance withthe present invention. As shown in FIG. 11, the heat exchanger 200 isdivided into separate regions dependent on the amount of heat producedalong the body of the heat source 99. The divided regions are separatedby the vertical intermediate layer 204 and/or microchannel wall features210 in the interface layer 202. However, it is apparent to one skilledin the art that the assembly shown in FIG. 11 is not limited to theconfiguration shown and is for exemplary purposes.

As shown in FIG. 3, the heat source 99 has a hot spot in location A anda warm spot, location B, whereby the hot spot in location A producesmore heat than the warm spot in location B. It is apparent that the heatsource 99 may have more than one hot spot and warm spot at any locationat any given time. In the example, since location A is a hot spot andmore heat in location A transfers to the interface layer 202 abovelocation A (designated in FIG. 11 as interface hot spot region A), morefluid and/or a higher rate of liquid flow is provided to interface hotspot region A in the heat exchanger 200 to adequately cool location A.It is apparent that although interface hot spot region B is shown to belarger than interface hot spot region A, interface hot spot regions Aand B, as well as any other interface hot spot regions in the heatexchanger 200, can be any size and/or configuration with respect to oneanother.

Alternatively, as shown in FIG. 11, the fluid enters the heat exchangervia fluid ports 208A is directed to interface hot spot region A byflowing along the intermediate layer 204 to the inflow conduits 205A.The fluid then flows down the inflow conduits 205A in the Z-directioninto interface hot spot region A of the interface layer 202. The fluidflows in between the microchannels 210A whereby heat from location Atransfers to the fluid by conduction through the interface layer 202.The heated fluid flows along the interface layer 202 in interface hotspot region A toward exit port 209A where the fluid exits the heatexchanger 200. It is apparent to one skilled in the art that any numberof inlet ports 208 and exit ports 209 are utilized for a particularinterface hot spot region or a set of interface hot spot regions. Inaddition, although the exit port 209A is shown near the interface layer202A, the exit port 209A is alternatively positioned in any otherlocation vertically, including but not limited to the manifold layer209B.

Similarly, in the example shown in FIG. 11, the heat source 99 has awarm spot in location B which produces less heat than location A of theheat source 99. Fluid entering through the port 208B is directed tointerface hot spot region B by flowing along the intermediate layer 204Bto the inflow conduits 205B. The fluid then flows down the inflowconduits 205B in the Z-direction into interface hot spot region B of theinterface layer 202. The fluid flows in between the microchannels 210 inthe X and Y directions, whereby heat generated by the heat source inlocation B is transferred into the fluid. The heated fluid flows alongthe entire interface layer 202B in interface hot spot region B upward toexit ports 209B in the Z-direction via the outflow conduits 205B in theintermediate layer 204 whereby the fluid exits the heat exchanger 200.

Alternatively, as shown in FIG. 9A, the heat exchanger 200 alternativelyincludes a vapor permeable membrane 214 positioned above the interfacelayer 202. The vapor permeable membrane 214 is in sealable contact withthe inner side walls of the heat exchanger 200. The membrane isconfigured to have several small apertures which allow vapor producedalong the interface layer 202 to pass therethrough to the outlet port209. The membrane 214 is also configured to be hydrophobic to preventliquid fluid flowing along the interface layer 202 from passing throughthe apertures of the membrane 214. More details of the vapor permeablemembrane 114 is discussed in co-pending U.S. application Ser. No.10/366,128, filed Feb. 12, 2003 and entitled, “VAPOR ESCAPE MICROCHANNELHEAT EXCHANGER” which is hereby incorporated by reference.

The microchannel heat exchanger of the present invention alternativelyhas other configurations not described above. For instance, the heatexchanger alternatively includes a manifold layer which minimizes thepressure drop within the heat exchanger in having separately sealedinlet and outlet apertures which lead to the interface layer. Thus,fluid flows directly to the interface layer through inlet apertures andundergoes thermal exchange in the interface layer. The fluid then exitsthe interface layer by flowing directly through outlet aperturesarranged adjacent to the inlet apertures. This porous configuration ofthe manifold layer minimizes the amount of distance that the fluid mustflow between the inlet and outlet ports as well as maximizes thedivision of fluid flow among the several apertures leading to theinterface layer.

The details of how the heat exchanger 100 as well as the individuallayers in the heat exchanger 100 are fabricated and manufactured arediscussed below. The following discussion applies to the preferred andalternative heat exchangers of the present invention, although the heatexchanger 100 in FIG. 3B and individual layers therein are expresslyreferred to for simplicity. It is also apparent to one skilled in theart that although the fabrication/manufacturing details are described inrelation to the present invention, the fabrication and manufacturingdetails also alternatively apply to conventional heat exchangers as wellas two and three-tier heat exchangers utilizing one fluid inlet port andone fluid outlet port as shown in FIGS. 1A-1C.

Preferably, the interface layer 102 has a coefficient of thermalexpansion (CTE) which is approximate or equal to that of the heat source99. Thus, the interface layer 102 preferably expands and contractsaccordingly with the heat source 99. Alternatively, the material of theinterface layer 102 has a CTE which is different than the CTE of theheat source material. An interface layer 102 made from a material suchas Silicon has a CTE that matches that of the heat source 99 and hassufficient thermal conductivity to adequately transfer heat from theheat source 99 to the fluid. However, other materials are alternativelyused in the interface layer 102 which have CTEs that match the heatsource 99.

The interface layer 102 in the heat exchanger 100 preferably has a highthermal conductivity for allowing sufficient conduction to pass betweenthe heat source 99 and fluid flowing along the interface layer 102 suchthat the heat source 99 does not overheat. The interface layer 102 ispreferably made from a material having a high thermal conductivity of100 W/m-K. However, it is apparent to one skilled in the art that theinterface layer 102 has a thermal conductivity of more or less than 100W/m-K and is not limited thereto.

To achieve the preferred high thermal conductivity, the interface layeris preferably made from a semiconductor substrate, such as Silicon.Alternatively, the interface layer is made from any other materialincluding, but not limited to single-crystalline dielectric materials,metals, aluminum, nickel and copper, Kovar, graphite, diamond,composites and any appropriate alloys. An alternative material of theinterface layer 102 is a patterned or molded organic mesh.

As shown in FIG. 12, it is preferred that the interface layer 102 iscoated with a coating layer 112 to protect the material of the interfacelayer 102 as well as enhance the thermal exchange properties of theinterface layer 102. In particular, the coating 112 provides chemicalprotection that eliminates certain chemical interactions between thefluid and the interface layer 102. For example, an interface layer 102made from aluminum may be etched by the fluid coming into contact withit, whereby the interface layer 102 would deteriorate over time. Thecoating 112 of a thin layer of Nickel, approximately 25 microns, is thuspreferably electroplated over the surface of the interface layer 102 tochemically pacify any potential reactions without significantly alteringthe thermal properties of the interface layer 102. It is apparent thatany other coating material with appropriate layer thickness iscontemplated depending on the material(s) in the interface layer 102.

In addition, the coating material 112 is applied to the interface layer102 to enhance the thermal conductivity of the interface layer 102 toperform sufficient heat exchange with the heat source 99, as shown inFIG. 12. For example, an interface layer 102 having a metallic basecovered with plastic can be thermally enhanced with a layer of Nickelcoating material 112 on top of the plastic. The layer of Nickel has athickness of at least 25 microns, depending on the dimensions of theinterface layer 102 and the heat source 99. It is apparent that anyother coating material with appropriate layer thickness is contemplateddepending on the material(s) in the interface layer 102. The coatingmaterial 112 is alternatively used on material already having highthermal conductivity characteristics, such that the coating materialenhances the thermal conductivity of the material. The coating material112 is preferably applied to the bottom surface 103 as well as themicrochannel walls 110 of the interface layer 102, as shown in FIG. 12.Alternatively, the coating material 112 is applied to either of thebottom surface 103 or microchannel walls 110. The coating material 112is preferably made from a metal including, but not limited to, Nickeland Aluminum. However, the coating material 112 is alternatively made ofany other thermally conductive material.

The interface layer 102 is preferably formed by an etching process usinga Copper material coated with a thin layer of Nickel to protect theinterface layer 102. Alternatively, the interface layer 102 is made fromAluminum, Silicon substrate, plastic or any other appropriate material.The interface layer 102 being made of materials having poor thermalconductivity are also coated with the appropriate coating material toenhance the thermal conductivity of the interface layer 102. One methodof electroforming the interface layer is by applying a seed layer ofchromium or other appropriate material along the bottom surface 103 ofthe interface layer 102 and applying electrical connection ofappropriate voltage to the seed layer. The electrical connection therebyforms a layer of the thermally conductive coating material 112 on top ofthe interface layer 102. The electroforming process also forms featuredimensions in a range of 10-100 microns. The interface layer 102 isformed by an electroforming process, such as patterned electroplating.In addition, the interface layer is alternatively processed byphotochemical etching or chemical milling, alone or in combination, withthe electroforming process. Standard lithography sets for chemicalmilling are used to process features in the interface layer 102.Additionally, the aspect ratios and tolerances are enhanceable usinglaser assisted chemical milling processes.

The microchannel walls 110 are preferably made of Silicon. Themicrochannel walls 110 are alternatively made of any other materialsincluding, but not limited to, patterned glass, polymer, and a moldedpolymer mesh. Although it is preferred that the microchannel walls 110are made from the same material as that of the bottom surface 103 of theinterface layer 102, the microchannel walls 110 are alternatively madefrom a different material than that of the rest of the interface layer102.

It is preferred that the microchannel walls 110 have thermalconductivity characteristics of at least 10 W/m-K. Alternatively, themicrochannel walls 110 have thermal conductivity characteristics of morethan 10 W/m-K. It is apparent to one skilled in the art that themicrochannel walls 110 alternatively have thermal conductivitycharacteristics of less than 10 W/m-K, whereby coating material 112 isapplied to the microchannel walls 110, as shown in FIG. 12, to increasethe thermal conductivity of the wall features 110. For microchannelwalls 110 made from materials already having a good thermalconductivity, the coating 112 applied has a thickness of at least 25microns which also protects the surface of the microchannel walls 110.For microchannel walls 110 made from material having poor thermalconductivity characteristics, the coating 112 has a thermal conductivityof at least 50 W/m-K and is more than 25 microns thick. It is apparentto one skilled in the art that other types of coating materials as wellas thickness dimensions are contemplated.

To configure the microchannel walls 110 to have an adequatethermal-conductivity of at least 10 W/m-K, the walls 110 areelectroformed with the coating material 112 (FIG. 12), such as Nickel orother metal, as discussed above. To configure the microchannel walls 110to have an adequate thermal conductivity of at least 50 W/m-K, the walls110 are electroplated with Copper on a thin metal film seed layer.Alternatively, the microchannel walls 110 are not coated with thecoating material. It is understood that the thermal conductivitycharacteristics of the microchannel walls 110 and the coating 112, whenappropriate, also apply to the pillars 203 (FIG. 10) and any appropriatecoating applied thereon.

The microchannel walls 110 are preferably formed by a hot embossingtechnique to achieve a high aspect ratio of channel walls 110 along thebottom surface 103 of the interface layer 102. The microchannel wallfeatures 110 are alternatively fabricated as Silicon structuresdeposited on a glass surface, whereby the features are etched on theglass in the desired configuration. The microchannel walls 110 arealternatively formed by a standard lithography techniques, stamping orforging processes, or any other appropriate method. The microchannelwalls 110 are alternatively made separately from the interface layer 102and coupled to the interface layer 102 by anodic or epoxy bonding.Alternatively, the microchannel features 110 are coupled to theinterface layer 102 by conventional electroforming techniques, such aselectroplating.

There are a variety of methods that can be used to fabricate theintermediate layer 104. The intermediate layer is preferably made fromSilicon. It is apparent to one skilled in the art that any otherappropriate material is contemplated including, but not limited toglass, laser-patterned glass, polymers, metals, glass, plastic, moldedorganic material or any composites thereof. Preferably, the intermediatelayer 104 is formed using plasma etching techniques. Alternatively, theintermediate layer 104 is formed using a chemical etching technique.Other alternative methods include machining, etching, extruding and/orforging a metal into the desired configuration. The intermediate layer104 is alternatively formed by injection molding of a plastic mesh intothe desired configuration. Alternatively, the intermediate layer 104 isformed by laser-drilling a glass plate into the desired configuration.

The manifold layer 106 is manufactured by a variety of methods. It ispreferred that the manifold layer 106 is fabricated by an injectionmolding process utilizing plastic, metal, polymer composite or any otherappropriate material, whereby each layer is made from the same material.Alternatively, as discussed above, each layer is made from a differentmaterial. The manifold layer 106 is alternatively generated using amachined or etched metal technique. It is apparent to one skilled in theart that the manifold layer 106 is manufactured utilizing any otherappropriate method.

The intermediate layer 104 is coupled to the interface layer 102 andmanifold layer 106 to form the heat exchanger 100 using a variety ofmethods. The interface layer 102, intermediate layer 104 and manifoldlayer 106 are preferably coupled to one another by an anodic, adhesiveor eutectic bonding process. The intermediate layer 104 is alternativelyintegrated within features of the manifold layer 106 and interface layer102. The intermediate layer 104 is coupled to the interface layer 102 bya chemical bonding process. The intermediate layer 104 is alternativelymanufactured by a hot embossing or soft lithography technique, whereby awire EDM or Silicon master is utilized to stamp the intermediate layer104. The intermediate layer 104 is then alternatively electroplated withmetal or another appropriate material to enhance the thermalconductivity of the intermediate layer 104, if needed.

Alternatively, the intermediate layer 104 is formed along with thefabrication of the microchannel walls 110 in the interface layer 102 byan injection molding process. Alternatively, the intermediate layer 104is formed with the fabrication of the microchannel walls 110 by anyother appropriate method. Other methods of forming the heat exchangerinclude, but are not limited to soldering, fusion bonding, eutecticBonding, intermetallic bonding, and any other appropriate technique,depending on the types of materials used in each layer.

Another alternative method of manufacturing the heat exchanger of thepresent invention is described in FIG. 13. As discussed in relation toFIG. 13, an alternative method of manufacturing the heat exchangerincludes building a hard mask formed from a silicon substrate as theinterface layer (step 500). The hard mask is made from silicon dioxideor alternatively spin-on-glass. Once the hard mask is formed, aplurality of under-channels are formed in the hard mask, wherein theunder-channels form the fluid paths between the microchannel walls 110(step 502). The under-channels are formed by any appropriate method,including but not limited to HF etching techniques, chemical milling,soft lithography and xenon difluoride etch. In addition, enough spacebetween each under-channel must be ensured such that under-channels nextto one another do not bridge together. Thereafter, spin-on-glass is thenapplied by any conventional method over the top surface of the hard maskto form the intermediate and manifold layers (step 504). Following, theintermediate and manifold layers are hardened by a curing method (step506). Once the intermediate and manifold layers are fully formed andhardened, one or more fluid ports are formed into the hardened layer(step 508). The fluid ports are etched or alternatively drilled into themanifold layer. Although specific methods of fabricating the interfacelayer 102, the intermediate layer 104 and manifold layer 106 arediscussed herein, other known methods known in art to manufacture theheat exchanger 100 are alternatively contemplated.

FIG. 14 illustrates an alternative embodiment of the heat exchanger ofthe present invention. As shown in FIG. 6, two heat exchangers 200, 200′are coupled to one heat source 99. In particular, the heat source 99,such as an electronic device, is coupled to a circuit board 96 and ispositioned upright, whereby each side of the heat source 99 ispotentially exposed. A heat exchanger of the present invention iscoupled to one exposed side of the heat source 99, whereby both heatexchangers 200, 200′ provide maximum cooling of the heat source 99.Alternatively, the heat source is coupled to the circuit boardhorizontally, whereby more than one heat exchanger is stacked on top ofthe heat source 99 (not shown), whereby each heat exchanger iselectrically coupled to the heat source 99; More details regarding thisembodiment are shown and described in co-pending U.S. patent applicationSer. No. 10/072,137, filed Feb. 7, 2002, entitled “POWER CONDITIONINGMODULE” which is hereby incorporated by reference.

As shown in FIG. 14, the heat exchanger 200 having two layers is coupledto the left side of the heat source 99 and the heat exchanger 200′having three layers is coupled to the right side of the heat source 99.It is apparent to one skilled in the art that the preferred oralternative heat exchangers are coupled to the sides of the heat source99. It is also apparent to one skilled in the art that the alternativeembodiments of the heat exchanger 200′ are alternatively coupled to thesides of the heat source 99. The alternative embodiment shown in FIG. 14allows more precise hot spot cooling of the heat source 99 by applyingfluid to cool hot spots which exist along the thickness of the heatsource 99. Thus, the embodiment in FIG. 14 applies adequate cooling tohot spots in the center of the heat source 99 by exchanging heat fromboth sides of the heat source 99. It is apparent to one skilled in theart that the embodiment shown in FIG. 14 is used with the cooling system30 in FIGS. 2A-2B, although other closed loop systems are contemplated.

As stated above, the heat source 99 may have characteristics in whichthe locations of one or more of the hot spots change due to differenttasks required to be performed by the heat source 99. To adequately coolthe heat source 99, the system 30 alternatively includes a sensing andcontrol module 34 (FIGS. 2A-2B) which dynamically changes the amount offlow and/or flow rate of fluid entering the heat exchanger 100 inresponse to a change in location of the hot spots.

In particular, as shown in FIG. 14, one or more sensors 124 are placedin each interface hot spot region in the heat exchanger 200 and/oralternatively the heat source 99 at each potential hot spot location.Alternatively, a plurality of heat sources are uniformly placed inbetween the heat source and heat exchanger and/or in the heat exchangeritself. The control module 38 (FIG. 2A-2B) is also coupled to one ormore valves in the loop 30 which control the flow of fluid to the heatexchanger 100. The one or more valves are positioned within the fluidlines, but are alternatively positioned elsewhere. The plurality ofsensors 124 are coupled to the control module 34, whereby the controlmodule 34 is preferably placed upstream from heat exchanger 100, asshown in FIG. 2. Alternatively, the control module 34 is placed at anyother location in the closed loop system 30.

The sensors 124 provide information to the control module 34 including,but not limited to, the flow rate of fluid flowing in the interface hotspot region, temperature of the interface layer 102 in the interface hotspot region and/or heat source 99 and temperature of the fluid. Forexample, referring to the schematic in FIG. 14, sensors positioned onthe interface 124 provide information to the control module 34 that thetemperature in a particular interface hot spot region in heat exchanger200 is increasing whereas the temperature in a particular interface hotspot region in heat exchanger 200′ is decreasing. In response, thecontrol module 34 increases the amount of flow to heat exchanger 200 anddecreases the amount of flow provided to heat exchanger 200′.Alternatively, the control module 34 alternatively changes the amount offlow to one or more interface hot spot regions in one or more heatexchangers in response to the information received from the sensors 118.Although the sensors 118 are shown with the two heat exchangers 200,200′ in FIG. 14, it is apparent that the sensors 118 are alternativelycoupled with only one heat exchanger.

The present invention has been described in terms of specificembodiments incorporating details to facilitate the understanding of theprinciples of construction and operation of the invention. Suchreference herein to specific embodiments and details thereof is notintended to limit the scope of the claims appended hereto. It will beapparent to those skilled in the art that modification s may be made inthe embodiment chosen for illustration without departing from the spiritand scope of the invention.

1. A heat exchanger comprising: a. an interface layer for cooling a heatsource, wherein the interface layer is configured to pass fluidtherethrough and the interface layer includes a thickness within a rangeof about 0.3 millimeters to about 1.0 millimeters; and b. a manifoldlayer for circulating fluid to and from the interface layer, themanifold layer having a first set fingers and a second set of fingers,wherein the first set of fingers are disposed in parallel with thesecond set of fingers and arranged to reduce pressure drop within theheat exchanger.
 2. The heat exchanger according to claim 1 wherein thefluid is in single phase flow condition.
 3. The heat exchanger accordingto claim 1 wherein the fluid is in two phase flow fluid conditions. 4.The heat exchanger according to claim 1 wherein at least a portion ofthe fluid undergoes a transition between single and two phase flowconditions in the interface layer.
 5. The heat exchanger according toclaim 1 wherein a particular finger in the first set is spaced apart byan appropriate dimension from a particular finger in the second set tominimize the pressure drop in the heat exchanger.
 6. The heat exchangeraccording to claim 1 wherein each of the fingers have the same lengthand width dimensions.
 7. The heat exchanger according to claim 1 whereinat least one of the fingers has a different dimension than the remainingfingers.
 8. The heat exchanger according to claim 1 wherein the fingersare arranged non-periodically in at least one dimension in the manifoldlayer.
 9. The heat exchanger according to claim 1 wherein at least oneof the fingers has at least one varying dimension along a length of themanifold layer.
 10. The heat exchanger according to claim 1 wherein themanifold layer includes more than three and less than 10 parallelfingers.
 11. The heat exchanger according to claim 1 wherein the fingersin the first set and second set are alternately disposed along adimension of the manifold layer.
 12. The heat exchanger according toclaim 1 wherein the manifold layer is configured to cool at least oneinterface hot spot region.
 13. The heat exchanger according to claim 1further comprising at least one first port in communication with thefirst set of fingers, wherein fluid enters the heat exchanger throughthe at least one first port.
 14. The heat exchanger according to claim13 further comprising at least one second port in communication with thesecond set of fingers, wherein fluid exits the heat exchanger throughthe at least one second port.
 15. The heat exchanger according to claim1 wherein the manifold layer is positioned above the interface layer,wherein fluid flows downward through the first set of fingers and upwardthough the second set of fingers.
 16. The heat exchanger according toclaim 13 further comprising a first port passage in communication withthe first port and the first set of fingers, the first port passageconfigured to channel fluid from the first port to the first set offingers.
 17. The heat exchanger according to claim 16 further comprisinga second port passage in communication with the second port and thesecond set of fingers, the second port passage configured to channelfluid from the second set of fingers to the second port.
 18. The heatexchanger according to claim 1 wherein the interface layer is integrallyformed with the heat source.
 19. The heat exchanger according to claim 1wherein the interface layer is coupled to the heat source.
 20. The heatexchanger according to claim 1 further comprising an intermediate layerfor channeling fluid to and from one or more predetermined positions inthe interface layer via at least one conduit, the intermediate layerpositioned between the interface layer and the manifold layer.
 21. Theheat exchanger according to claim 20 wherein the intermediate layer iscoupled to the interface layer and the manifold layer.
 22. The heatexchanger according to claim 20 wherein the intermediate layer isintegrally formed with the interface layer and the manifold layer. 23.The heat exchanger according to claim 20 wherein the at least oneconduit has at least one varying dimension along the intermediate layer.24. The heat exchanger according to claim 1 wherein the interface layerincludes a coating thereupon, wherein the coating provides anappropriate thermal conductivity of at least 10 W/m-K.
 25. The heatexchanger according to claim 1 wherein the interface layer has a thermalconductivity of at least 100 W/m-K.
 26. The heat exchanger according toclaim 1 further comprising a plurality of pillars configured in apredetermined pattern along the interface layer.
 27. The heat exchangeraccording to claim 26 wherein at least one of the plurality of pillarshas an area dimension within the range of and including (10 micron)² and(100 micron)².
 28. The heat exchanger according to claim 26 wherein atleast one of the plurality of pillars has a height dimension within therange of and including 50 microns and 2 millimeters.
 29. The heatexchanger according to claim 26 wherein at least two of the plurality ofpillars are separate from each other by a spacing dimension within therange of and including 10 to 150 microns.
 30. The heat exchangeraccording to claim 26 wherein the plurality of pillars include a coatingthereupon, wherein the coating has an appropriate thermal conductivityof at least 10 W/m-K.
 31. The heat exchanger according to claim 1wherein the interface layer has a roughened surface.
 32. The heatexchanger according to claim 1 wherein the interface layer includes amicro-porous structure disposed thereon.
 33. The heat exchangeraccording to claim 32 wherein the porous microstructure has a porositywithin the range of and including 50 to 80 percent.
 34. The heatexchanger according to claim 32 wherein the porous microstructure has anaverage pore size within the range of and including 10 to 200 microns.35. The heat exchanger according to claim 32 wherein the porousmicrostructure has a height dimension within the range of and including0.25 to 2.00 millimeters.
 36. The heat exchanger according to claim 1further comprises a plurality of microchannels configured in apredetermined pattern along the interface layer.
 37. The heat exchangeraccording to claim 36 wherein at least one of the plurality ofmicrochannels has an area dimension within the range of and including(10 micron)² and (100 micron)².
 38. The heat exchanger according toclaim 36 wherein at least one of the plurality of microchannels has aheight dimension within the range of and including 50 microns and 2millimeters.
 39. The heat exchanger according to claim 36 wherein atleast two of the plurality of microchannels are separate from each otherby a spacing dimension within the range of and including 10 to 150microns.
 40. The heat exchanger according to claim 36 wherein at leastone of the plurality of microchannels has a width dimension within therange of and including 10 to 100 microns.
 41. The heat exchangeraccording to claim 36 wherein the plurality of microchannels are coupledto the interface layer.
 42. The heat exchanger according to claim 36wherein the plurality of microchannels are integrally formed with theinterface layer.
 43. The heat exchanger according to claim 36 whereinthe plurality of microchannels are divided into segmented arrays with atleast one groove disposed therebetween, wherein the at least one grooveis aligned with a corresponding finger.
 44. The heat exchanger accordingto claim 36 wherein the plurality of microchannels include a coatingthereupon, wherein the coating has an appropriate thermal conductivityof at least 10 W/m-K.
 45. The heat exchanger according to claim 1wherein an overhang dimension is within the range of and including 0 to15 millimeters.
 46. A heat exchanger for cooling a heat sourcecomprising: a. a manifold layer including a first set of fingers in afirst configuration, wherein each finger in the first set channels fluidat a first temperature, the manifold layer further including a secondset of fingers in a second configuration, wherein each finger in thesecond set channels fluid at a second temperature, the first set andsecond set of fingers arranged parallel to each other; and b. aninterface layer including a thickness within a range of about 0.3 to 1.0millimeters, and configured to receive fluid at the first temperature ata plurality of first locations, wherein each first location isassociated with a corresponding finger in the first set, the interfacelayer passing fluid along a plurality of predetermined paths to aplurality of second locations, wherein each second location isassociated with a corresponding finger in the second set.
 47. The heatexchanger according to claim 46 wherein the fluid is in single phaseflow conditions.
 48. The heat exchanger according to claim 46 whereinthe fluid is in two phase flow conditions.
 49. The heat exchangeraccording to claim 46 wherein at least a portion of the fluid undergoesa transition between single and two phase flow conditions in theinterface layer.
 50. The heat exchanger according to claim 46 wherein aparticular finger in the first set is spaced apart by an appropriatedimension from a particular finger in the second set, wherein theappropriate dimension reduces the pressure drop in the heat exchanger.51. The heat exchanger according to claim 46 further comprising at leastone first port in communication with the first set of fingers, whereinfluid enters the heat exchanger through the at least one first port. 52.The heat exchanger according to claim 51 further comprising at least onesecond port in communication with the second set of fingers, whereinfluid exits the heat exchanger through the at least one second port. 53.The heat exchanger according to claim 46 wherein the manifold layer ispositioned above the interface layer, wherein fluid flows downwardthrough the first set of fingers and upward through the second set offingers.
 54. The heat exchanger according to claim 46 wherein theinterface layer is integrally formed with the heat source.
 55. The heatexchanger according to claim 46 wherein the interface layer is coupledto the heat source.
 56. The heat exchanger according to claim 46 whereinthe fingers in the first set are positioned in an alternatingconfiguration with the fingers in the second set.
 57. The heat exchangeraccording to claim 46 wherein each of the fingers have the same lengthand width dimensions.
 58. The heat exchanger according to claim 46wherein at least one of the fingers has a different dimension than theremaining fingers.
 59. The heat exchanger according to claim 46 whereinthe fingers are arranged non-periodically in at least one dimension inthe manifold layer.
 60. The heat exchanger according to claim 46 whereinat least one of the fingers has at least one varying dimension along alength of the manifold layer.
 61. The heat exchanger according to claim46 wherein the manifold layer includes more than three and less than 10parallel fingers.
 62. The heat exchanger according to claim 52 furthercomprising a first port passage in communication with the first port andthe first set of fingers, the first port passage configured to channelfluid from the first port to the first set of fingers.
 63. The heatexchanger according to claim 62 further comprising a second port passagein communication with the second port and the second set of fingers, thesecond port passage configured to channel fluid from the second set offingers to the second port.
 64. The heat exchanger according to claim 46further comprising an intermediate layer for channeling fluid to andfrom one or more predetermined positions in the interface layer via atleast one conduit, the intermediate layer positioned between theinterface layer and the manifold layer.
 65. The heat exchanger accordingto claim 64 wherein the conduit is arranged in a predeterminedconfiguration to channel fluid to one or more interface hot spot regionsin the interface layer.
 66. The heat exchanger according to claim 64wherein the conduit is arranged in a predetermined configuration tochannel fluid from one or more interface hot spot regions in theinterface layer.
 67. The heat exchanger according to claim 64 whereinthe intermediate layer is coupled to the interface layer and themanifold layer.
 68. The heat exchanger according to claim 64 wherein theintermediate layer is integrally formed with the interface layer and themanifold layer.
 69. The heat exchanger according to claim 64 wherein theconduit has at least one varying dimension in the intermediate layer.70. The heat exchanger according to claim 46 wherein the interface layerincludes a coating thereupon, wherein the coating provides anappropriate thermal conductivity of at least 10 W/m-K.
 71. The heatexchanger according to claim 46 wherein the interface layer has athermal conductivity is at least 100 W/m-K.
 72. The heat exchangeraccording to claim 46 further comprising a plurality of pillarsconfigured in a predetermined pattern along the interface layer.
 73. Theheat exchanger according to claim 72 wherein at least one of theplurality of pillars has an area dimension within the range of andincluding (10 micron)² and (100 micron)².
 74. The heat exchangeraccording to claim 72 wherein at least one of the plurality of pillarshas a height dimension within the range of and including 50 microns and2 millimeters.
 75. The heat exchanger according to claim 72 wherein atleast two of the plurality of pillars are separate from each other by aspacing dimension within the range of and including 10 to 150 microns.76. The heat exchanger according to claim 72 wherein the plurality ofpillars include a coating thereupon, wherein the coating has anappropriate thermal conductivity of at least 10 W/m-K.
 77. The heatexchanger according to claim 46 wherein the interface layer has aroughened surface.
 78. The heat exchanger according to claim 46 whereinthe interface layer includes a microporous structure disposed thereon.79. The heat exchanger according to claim 78 wherein the porousmicrostructure has a porosity within the range of and including 50 to 80percent.
 80. The heat exchanger according to claim 78 wherein the porousmicrostructure has an average pore size within the range of andincluding 10 to 200 microns.
 81. The heat exchanger according to claim78 wherein the porous microstructure has a height dimension within therange of and including 0.25 to 2.00 millimeters.
 82. The heat exchangeraccording to claim 46 further comprises a plurality of microchannelsconfigured in a predetermined pattern along the interface layer.
 83. Theheat exchanger according to claim 82 wherein at least one of theplurality of microchannels has an area dimension within the range of andincluding (10 micron)² and (100 micron)².
 84. The heat exchangeraccording to claim 82 wherein at least one of the plurality ofmicrochannels has a height dimension within the range of and including50 microns and 2 millimeters.
 85. The heat exchanger according to claim82 wherein at least two of the plurality of microchannels are separatefrom each other by a spacing dimension within the range of and including10 to 150 microns.
 86. The heat exchanger according to claim 82 whereinat least one of the plurality of microchannels has a width dimensionwithin the range of and including 10 to 100 microns.
 87. The heatexchanger according to claim 82 wherein the microchannels are coupled tothe interface layer.
 88. The heat exchanger according to claim 82wherein the microchannels are integrally formed with the interfacelayer.
 89. The heat exchanger according to claim 82 wherein themicrochannels are divided into segments along a dimension of theinterface layer, at least one groove disposed in between the dividedmicrochannel segments.
 90. The heat exchanger according to claim 82wherein the microchannels are continuous along a dimension of theinterface layer.
 91. The heat exchanger according to claim 89 whereinthe at least one groove is aligned with a corresponding finger.
 92. Theheat exchanger according to claim 82 wherein the plurality ofmicrochannels include a coating thereupon, wherein the coating has anappropriate thermal conductivity of at least 10 W/m-K.
 93. The heatexchanger according to claim 46 wherein an overhang dimension is withinthe range of and including 0 to 15 millimeters.